Hardware breaks. Software has defects. Viruses propagate. Buildings catch fire. Power fails. People make mistakes. Although it is preferred that these events never occur, it is prudent to defend against them. The cost of data unavailability can be large. Many businesses estimate their outage costs as more than $250,000/hour. Others estimate outage costs at more than $ 1,000,000/hour. The price of data loss is even higher. Recent high-profile disasters have raised awareness to plan for recovery or continuity.
A constant challenge is to construct dependable systems that protect data and the ability to access data. Data is an asset to substantially all businesses. Losing information due to various failures can bring a company to its knees—or put it out of business altogether. Such catastrophic outcomes can readily be prevented using various configurations of hardware and software; however, the design space of results, such as solutions, is surprisingly large, and there are a myriad of configuration choices. In addition, the various alternative design choices interact in complicated ways. Thus, results, such as solutions, are often over-engineered or under-engineered, and administrators may not understand the degree of dependability they provide.
It is difficult to combine and configure the building blocks for data protection to create well-engineered data dependability results, such as solutions. Over-engineered results, such as solutions, may incur excessive costs to defend against negligible risks. Under-engineered results, such as solutions, have their own costs in a disaster: crippling outages, loss of critical data, or unacceptably degraded service. Faced with these choices, designers often resort to ad hoc approaches to strike the right balance, guided by rules of thumb and their own limited or even irrelevant experience. When a designer resorts to an ad hoc approach, many potential results may not be considered. Therefore, the selected result may not be as appropriate, well-matched, and/or optimal as when more results are considered.